A Comparison of Platinized Grooved Electrode Performance with Ring‐Tip Electrodes

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Abstract
One of the determinants of the capture threshold of an endocardial pacing lead is the configuration of the electrode tip. To evaluate whether micro‐ and macroporous electrodes have better initial and chronic thresholds than nonporous electrodes, acute and chronic capture thresholds, stimulation impedance and sensing thresholds were determined in 22 patients in whom a ventricular ring‐tip electrode and a unipolar, dual chamber pacemaker with bidirectional teiemetry had been implanted. These values were compared to those obtained from 25 patients receiving an electrode constructed with a platinized groove surface at the time of implant of an identical pulse generator. The ventricular capture threshold at implant was 0.7 V ± 0.3 at 0.6 msec pulse width for both groups. The capture threshold was significantly greater in the ring tip electrode group at follow‐up periods of 1 month (1.1 V ± O.5 vs 1.6 V ± 0.6, P < 0.008), 4 months (1.0 V ± 0.2 vs 1.7 V ± 0.8. P < 0.002), and 10 months (1.2 V ± 0.4 vs 1.7 V ± 0.5, P < 0.04) following implantation. The stimulation impedance at the time of implantation was lower in the ring‐tip electrode group (530 ohms vs 603 ohms, P < 0.03), but thereafter no significant difference was seen between the two groups. The acute and chronic sensing threshoids ivere similar in both groups. While the microporous electrode had significantly lower chronic capture threshoids, the magnitude of this difference is small, and probably clinically inconsequential. Since three patients with ring‐tip electrodes and two patients with microporous electrodes had at least one chronic threshold exceeding 2.5 V, periodic threshold determination is prudent in all patients.